Inserter systems, such as those applicable for use with the present invention, are mail processing machines typically used by organizations such as banks, insurance companies and utility companies for producing a large volume of specific mailings where the contents of each mail item are directed to a particular addressee.
In many respects, the typical inserter system resembles a manufacturing assembly line. Sheets and other raw materials (other sheets, enclosures, and envelopes) enter the inserter system as inputs. Then, a variety of modules or workstations in the inserter system work cooperatively to process the sheets until a finished mail piece is produced. The exact configuration of each inserter system depends upon the needs of each particular customer or installation.
Typically, inserter systems prepare mail pieces by gathering collations of documents on a conveyor. The collations are then transported on the conveyor to an insertion station where they are automatically stuffed into envelopes. After being stuffed with the collations, the envelopes are removed from the insertion station for further processing. Such further processing may include automated closing and sealing the envelope flap, weighing the envelope, applying postage to the envelope, and finally sorting and stacking the envelopes.
The input stages of a typical inserter system are depicted in FIG. 1a. Rolls or stacks of continuous printed documents, called a web, are provided at a web supply and fed into a web cutter where the continuous web is cut into individual sheets. In some inserter systems, the input stages of an inserter also include a right-angle turn to allow the individual pages to change their moving direction before they are fed into the inserter, as shown in FIG. 1b. 
In general, the web material is driven in move-and-pause cycles, wherein the web material is temporarily paused for a short period to allow the cutter to cut the material into cut sheets. Thus, in each cycle, the web must be accelerated and decelerated.
FIG. 2 illustrates the input stages of an inserter system. As shown in FIG. 2, the web material 5 is driven continuously by a web driver 100 into a web-cutting module 200. The web-cutting module 200 has a cutter 210, usually in a form of a guillotine cutting blade, to cut the web material 5 crosswise into separate sheets 8.
According to current technology, there is no way of knowing if a blade set is approaching failure in the field, until the blade set actually fails. Blades are either changed at failure, thereby disrupting the mailing operation, or the blades are replaced regularly without knowledge of the actual condition of the blade set.
Guillotine cutter blades for high speed paper processing have a finite life before they become so dull that they either stop cutting paper or stop cutting reliably. Field data varies widely for blade life, and is heavily dependent upon how well the cutter is set up and maintained. Collected field data show that blade set life ranges anywhere between 5 million and 25 million cycles before a blade needs to be replaced, or removed to be re-sharpened. Blade failure during a large production mail run is highly undesirable and can cause major disruption to production mailing operations. This is especially true for those machines producing time-sensitive mail, such as end of month bills and financial statements. Often, blades are replaced long before they are near failing, during a scheduled preventative maintenance procedure to avoid such situations. Although typical blade sets are expensive and machine downtime and labor adds additional expenditure to replace them, it is more cost effective to replace them early rather than risk downtime due to failed blade sets during a live mail run.
It would be helpful to have a way to find out whether a blade set is near failure in the field, before the failure actually occurs. Often, blade failure occurs when the blade edges in a cutter become sufficiently rounded, scored or nicked, as seen through a high powered microscope. It is conjectured that blades stop reliably cutting paper when the edge radius of the blade exceeds one thousandth of an inch, whereas the blade radius specification for a new high speed cutter blade will typically not exceed one half of one thousandth of an inch.
FIG. 3 is a side view of the blade slider-crank mechanism, with key crank displacements noted for a 360-degree crank blade cycle. The blade assembly contains the upper movable blade that is pinned to the connecting rod. Not shown are two low blades that are fixed in the vertical direction but are spring loaded horizontally against each side of the upper blade. The crank mechanism is homed at zero degrees or TDC (top-dead center). Once commanded to cut, the blade begins to move downward, and contacts the inner sheet at crank displacement, A. At crank positions E, the blade has completed the cut.
FIG. 4 shows the geometry of the upper blade when the blade is located at crank Top Dead Center (TDC), where alpha (%) is the blade shear angle. At TDC, the spring loaded blades are held apart by the tab, which is integral to the blade construction. Again, as the crank rotates, the blade translates downward and this motion in conjunction with the shear angle produces a scissors effect with the lower blades and begins to cut the paper web when the upper blade makes contact with the paper at the stationary lower blade line (reference displacement, A, in FIG. 3).
The crank is coupled to a servo motor. For each blade cycle, the crank executes 360 degrees of motion. During normal cutting operation, the blade is commanded to follow a velocity profile that is typically executed in 45 milliseconds.